(CBS)Season 21 of "The Amazing Race" is coming to a close on Sunday (Dec. 9), and host Phil Keoghan promises a wild finale.

"The finale is an all-out sprint to the finish line!" Keoghan tells Zap2it. "It's pretty insane. We have a terrifying Houdini-inspired Roadblock in New York, where teams are hanging 15 stories above the Brooklyn Navy Yard...and much more.

"But it's not so much about the challenges that the teams will encounter in the final leg as it is about the mental stress that they have to endure. In the previous legs, the only thing they needed to worry about was not coming in last. Now, it's imperative that they come in first. No room for error."

But often in "TAR," teams have no control over the game -- such as the travel mishaps experienced by Abbie and Ryan, who were on track to be the Race's first $2 million winners.

"I always feel bad for any team that has back luck or makes disastrous decisions," admits Keoghan, "but I also get excited about what the unpredictable elements of the Race provides in terms of entertainment. Every good story has to have an adversary, a struggle and emotional highs and lows."

It's been a roller-coaster ride for all the finalists. Here's how Keoghan compares his initial impressions of the teams versus how they performed in the Race:

Trey and Lexi: "I initially predicted that they would suffer from their lack of travel experience, but there's no doubt they have exceeded everyone's expectations, and perhaps even their own. Whatever happens they should be very proud of their accomplishments. They have an extremely strong relationship and are clearly a perfect match."

Jaymes and James: "I thought they would underestimate just how challenging this Race would be. They prove that you really cannot judge a book by its cover. They made racing fun and I think they've picked up some new Chippendale fans along the way."

Josh and Brent: "I really misjudged the willpower of these two and I have a feeling many other people have in the past. They have an inner strength that they have shown in the most challenging circumstances. When I saw Brent collapse on the mat in Bangladesh, I was almost certain their Race was over.

Natalie and Nadiya: My initial impression matched how they performed in this Race...Loud."

"With all due respect, I did not think that the Beekmans would be in the finale," he admitted. "I thought my predictions were right during their breakdown in Bangladesh ... as well as their overall performance having not won a single leg.

"That said, they have beat out some very strong teams," Keoghan notes, "and as always on 'The Amazing Race' ... anything can happen."

The Amazing Race - Phil Keoghan InterviewAndrew Freund catches up with Host, Phil Keoghan, on the blue carpet, as the stars of CBS get together to celebrate the new Fall season. Watch The Amazing Race this Fall, Sundays at 8/7c. Only CBS!